1. Field of the Invention
This invention relates to trimming devices, and particularly to trimming devices mounted on stern drive motors for power boats, such as inboard-outboard and outboard motors, substantially within the slipstream of the propeller.
2. Description of the Prior Art
It is commonly known that the attitude angle of a power boat is important for its performance. If the bow is riding too high or too low, the power required is greater than if the attitude had been somewhere inbetween. Hence, there exists an attitude angle that gives the best cruise performance and economy for each speed. There are on the market today several devices to accomplish attitude control.
It is known to control the attitude of boats by use of trim tabs mounted onto the stern of the boat. Examples of patented trim tabs are disclosed by U.S. Pat. No. 3,001,499, granted Sept. 26, 1961, to Joseph H. Jacobs and Marcellus L. Jacobs; U.S. Pat. No. 3,046,928, granted July 31, 1962, to John F. Sherrill; U.S. Pat. No. 3,062,167, granted Nov. 6, 1962, to Charles H. Bennett; U.S. Pat. No. 3,177,837, granted Apr. 13, 1965, to John F. Sherrill; U.S. Pat. No. 3,298,344, granted Jan. 17, 1967, to Robert E. Yunker and John T. Southern; and U.S. Pat. No. 3,463,109, granted Aug. 26, 1969, to Howard E. Weiler.
An example of apparatus for vertically trimming an outdrive type power boat by adjusting the outdrive to change the angle of the propeller thrust vector relative to boat is disclosed in U.S. Pat. No. 3,842,789, granted Oct. 22, 1974 to Karl A. Bergstedt. The trim control of some boats equipped with stern drives or outboard motors is performed by changing the direction of the propeller thrust vector in a vertical plane. This means that the control device has to overcome the reaction force created by the propeller thrust. In all known cases the control is assisted by electrical or hydraulic power.
Known trimming apparatuses in the nature of one or more horizontal vanes positioned closely adjacent a propeller and adjustable in angle about a horizontal axis are disclosed by the folliwing U.S. Pat. Nos. 1,529,036, granted Mar. 10, 1925to Clarence F. Richey; 2,099,492, granted Nov. 16, 1937, to Alfred E. Luders; No. 2,705,468, granted Apr. 5, 1955, to Sidney Dix; 3,120,829, granted Feb. 11, 1964, to Wilson W. Chew and Willis G. Stewart; 3,199,483, granted Aug. 10, 1965, to Floyd P. Ellzey; 3,433,195, granted Mar. 18, 1969, to Charles W. Poole and 3,804,048, granted Apr. 16, 1974, to David J. Cline.